Given time, they will disappear. The deeper grooves will take longer, of course.

_________________Jim Lewis - lewisjk@windstream.net - Western NC - People, when Columbus discovered this country, it was plumb full of nuts and berries. And I'm right here to tell you the berries are just about all gone. Uncle Dave Macon, old-time country musician

in answer to your second question, no rule of thumb, but when a tree is in a very active growth period, you really have to stay on top of it and remove the wire at the first sign of it cutting in... less so during "sleepy" times for the trees.

(i'm not a pine guy but i hear that some wire scarring on pines can be more acceptable as it adds character as the bark later grows...)

and this is something i have a hard time with because it seems wasteful, but do not try to un-wind the wire for re-use (unless you can do so without flexing the tree)... in other words you don't want to un-do what has been done by flexing the tree and re-breaking the cells that have set in the new bends... so, best to always cut the wire off (i keep a tray of scrap wire for small jobs).